In recent years, reflective liquid crystal on silicon (LCOS) imagers are widely employed for projection displays of various sizes, from professional projection for theaters and home entertainment to portable micro to pico projection in handheld electronics devices.
The basic planar components of a LCOS imager include a top cover, planar liquid crystal cell and an active matrix backplane. The top cover glass is generally provided with a transparent conductive film, which is most commonly made from transparent conductive material, such as indium tin oxide (ITO). The active matrix backplane takes a silicon substrate as a backplane substrate, and a reflective pixilated-electrode array is formed on the backplane substrate. The planar liquid crystal cell is sandwiched between the transparent conductive film and the reflective pixilated-electrode array. Spatial modulation by such a LCOS imager takes effect on particular polarized illumination oriented relative to the liquid crystal cell, for example, on the light portion of P-polarization, while little on the counterpart of S-polarization orthogonal to the P-polarized light potion. Though in general illumination to a LCOS imager is pre-polarized, still illumination contains residual light portion of S-polarization being reflected back without modulation, which might lead to loss in contrast ratio when the LCOS image is used for projection display.